I have no answers to your specific questions, but I think that F9 flights may have been and will be extremely full, both last week and this week due to Spring Break. Last Thursday, I tried to get an earlier flight from DFW to DEN, and not only were both earlier flights sold out, but also the flight for which I had a reservation. As you know, this is a bit unusual for Thursday. I usually have had no problem getting reassigned on the same day on F9.

The Gate Agent verified that Spring Break was filling planes. That may have an impact on your attempt to get a reward ticket. More than likely the flight you are ticketed for will be completely filled, too.